1. Field of the Invention
This invention relates to the field of cutting wheels useful for grinding tree stumps. More specifically, it relates to a stump cutter assembly and the component parts thereof.
2. Description of the Related Art
It is known to provide a stump grinding apparatus to cut and dispose of tree stumps. The device finds use for agricultural applications, for proper lawn maintenance and care, and for site development. It is often required to lower a protruding stump to a level that is below grade so that it will not interfere with plowing, disking and other farm tasks. For pleasing appearance of residential lawns, stumps of dead and fallen trees must likewise be cut away to a point that is below grade to allow for soil to be placed thereover for seeding or planting. When used for site development, the apparatus permits soil to be moved as needed. Typically, such a device includes a rotatable grinding wheel having a plurality of cutting teeth disposed circumferentially about the wheel. The wheel can be powered by a chain drive, or by gear or belt, or may be at the end of a movable boom driven by a diesel or gasoline engine. The cutting teeth of the stump grinders commonly encounter more than just wood when performing their tasks. They are brought into contact with rocks and all manner of buried debris, such as re-bar, wire, cinder block and other materials of construction. Because of these hidden obstacles, the teeth are subject to considerable wear and breakage, and the peripheral surface of the cutting wheel experiences considerable wear as well.
The present invention relates to a stump cutting wheel assembly. The assembly comprises a wheel having a plurality of recesses spaced around the circumference thereof. A replaceable cutter block is inserted into each recess and is secured to the wheel. The block has a leading surface and a trailing surface, two sides co-linear with the sides of the wheel, a top with a radius of curvature corresponding to that of the cutting wheel, and a bottom surface corresponding to the surfaces of the recess. A plurality of cutting teeth, each having a shank, are removably inserted into holes in the cutter block and/or the sides of the wheel. Each shank has a free end and an abutment end, the abutment end terminating in a rearwardly extending shoulder that co-operates with the block to serve as a stop to limit linear and rotational movement of the shank in the block or the wheel. An extension on the tooth projects rearwardly of the tooth face to rest against the adjacent surface of a block or the wheel to provide additional support for the tooth to resist shock and bending moments. The cutting wheel is a split wheel having a first half and a second halfjoined to one other along the diametric surface thereof, each half having a semicircular cut-out in the diametric surface to permit the wheel to be mounted around a hub keyed on a drive shaft. The two halves of the wheel are joined together using clamping means comprising a pair of butterfly clamps. Each butterfly clamp fits in corresponding slots in both halves of the wheel. The clamp engages a bolt extending from the semicircular periphery along mating kerfs in the diametric surfaces. Preferably, the end of the kerfs immediately radially inward of the periphery is enlarged to form a shoulder which receives a sleeve through which the bolt passes.
Each cutter block includes means cooperating with a corresponding recess in the peripheral surface of the wheel to align the blocks with the rotational direction of the wheel. The cooperating means includes a slot in the bottom of the recess, a corresponding slot in the bottom surface of the block and a key aligning the two slots. The back surface of each recess forms an undercut angle, and the trailing surface of the block is co-planar therewith. A hole extends through each block from the top surface of the block to the bottom surface, and a threaded fastener such, as a bolt, passes through the hole for fastening the block into the recess of the cutting wheel. The bolt is threaded into a nut plate disposed in a slot in the wheel radially beneath the block. A generally V-shaped groove is formed between the front wall of the recess and the leading edge of the block, and a wedge is located between the two walls of the groove, and is secured to said nut plate with a second threaded fastener. The shank on each tooth includes a circumferential groove, and a spring clip or a spring pin engages the groove to anchor the tooth in a corresponding hole in the block or in the wheel.
The invention further relates to a split wheel for a stump grinder. The split wheel comprises a first half and a second half joined to one another along the diametric surfaces thereof. Each half has an axially positioned semicircular cut-out that allows the two halves to be assembled together. The two halves are assembled on a conventional hub using a pair of clamps, such as butterfly clamps. A slot is located inboard of the semicircular periphery of each half and extends in from each mating plane to receive one clamp. A groove along the mating surface joins each slot to the semicircular periphery to receive a bolt extending in from the periphery and threaded into one of the clamps to hold the two halves together. The groove includes a shoulder recessed beneath the peripheral surface to receive a sleeve which, in turn, receives the head of the bolt.
The split wheel further includes a plurality of recesses in the periphery thereof, each recess shaped to receive a removable cutter block. Each recess has a front edge, a bottom edge and a rear edge. A threaded block fastener is located near the front edge. The rear edge is undercut to conform to the trailing surface of the block. A circumferentially extending slot in the bottom of the recess is adapted to receive an alignment key engageable with a corresponding slot in the bottom of each block. The threaded block fastener comprises a slot radially inwardly of each recess, and a nut plate in the slot having a threaded hole to receive the block fastener. The nut plate includes a second threaded hole to receive a threaded fastener extending through a block wedge. Each half of the wheel includes a semicircular cut-out along the diametric surface on either side of the axially positioned cut-out, forming a non-axially located circular hole with the corresponding cut-out in the other half. A conventional mounting hub comprises two flanges bolted on either side of the wheel. A pair of holes extends through the two flanges aligned with the two non-axial holes in the wheel, and drive pins extends through these holes in the mounting hub. The mounting hub includes a keyway for mounting the wheel on the drive shaft.
The invention also relates to a replaceable cutter block adapted to be inserted into a recess in the periphery of the cutting wheel for a stump grinder. The cutter block has a top surface with a radius of curvature corresponding to the outer periphery of the cutting wheel. The block also includes a bottom surface that is co-planar with the bottom of the recess, two parallel side surfaces, a leading surface and a trailing surface. The trailing surface corresponds to the rear surface of the recess. At least one hole in the block receives a removable cutting tooth, the hole extending from the top surface or a side surface at an angle of inclination from the said surface toward the back surface of a block. The hole extends into the block toward the trailing surface at an angle of between about 30xc2x0 and about 60xc2x0. The block includes means, such as a slotted key way adapted to receive a key extending longitudinally along the bottom thereof, to engage a corresponding alignment means in the bottom of the recess. A threaded fastener secures the block into the recess of the cutting wheel. This fastener comprises a bolt adapted to be threaded into a nut plate positioned in a slot within the cutting wheel radially beneath the block. The trailing surface of the block conforms to the rear wall of the recess and has an angle of less than 90xc2x0 but greater than about 60xc2x0 with respect to the bottom of the block.
The invention further comprises a cutting tooth to be removably engaged with a stump cutting wheel or a block on the circumference of such a wheel. The tooth comprises a planar cutting surface adapted to form an angle generally orthogonal to a side or a top of said block when the tooth is engaged therewith. It also includes a shank to be inserted into a corresponding hole in the block, said shank having a free end and an abutment end. The abutment end terminates in a shoulder formed at right angles to the shank and adapted to cooperate with the block to serve as a stop to limit the linear and rotational movement of the shank into the block. An extension projects rearwardly of the tooth face and is adapted to rest against the planar side or top surface of a block when the tooth is inserted into the block, said extension serving to provide a support for the tooth when in use. The shank typically includes a circumferentially extending groove and a spring clip engaging the groove for the purpose of providing a compressive fit of the tooth in the corresponding hole in a block. The shank forms an interior angle of between about 30xc2x0 and about 60xc2x0, preferably about 45xc2x0, with respect to the cutting face of the tooth. The angle corresponds to the diagonal angle in the block or cutting wheel so as to provide the proper cutting angle for the face when the tooth is properly mounted.